VATICAN CITY 
His arms outstretched in a symbolic embrace, Pope Benedict XVI blessed tens of thousands of cheering people on Sunday in one of his last appearances as pontiff from his window overlooking St. Peter's Square.

Last week, 85-year-old Benedict shocked the world by announcing his resignation. He will step down on Feb. 28, planning to retreat to a life of prayer in a monastery behind the Vatican's ancient walls.

The noontime appointment in the vast cobblestone square also served as a kind of trial run for how Rome will handle the logistics, including crowd security, as the city braces for faithful to flock to Rome for the election and installation of the cardinal who will succeed Benedict as leader of the world's 1.2 billion Catholics.

Rome Mayor Gianni Alemanno said upward of 100,000 people turned out Sunday and that everything went smoothly. But while there was still space in St. Peter's Square for more, many couldn't get in — or easily out — because entrances from the main boulevard were just too narrow.

The huge crowd — including parents with babies in carriages and strollers, elderly people using canes, and the disabled in wheelchairs — tried to squeeze through two spaces police left open in the metal barricades edging the square. Some people panicked or called out to police to help them get in or out of the square.

Pilgrims and tourists had an easier time if they entered through spaces in the elegant colonnade that architect Gianlorenzo Bernini designed to cradle the sides of the St. Peter's Square.

Benedict seemed touched by the outpouring of affection after his decision to go down in history as the first pontiff in some 600 years to resign. The pontiff told cardinals last week that he no longer has the mental and physical stamina to vigorously shepherd the church.

Looking into hazy sunshine Sunday, he smiled shyly at the sight of the crowd below, filled with pilgrims waving their countries' flags and holding up banners with words of support. One group of Italians raised a banner which read: "We love you."

Speaking in Italian, the pope told the cheering crowd: "Thanks for turnout in such numbers! This, too, is a sign of the affection and the spiritual closeness that you are giving me in these days." He stretched out his arms as if to embrace the faithful from across the vast expanse of the square.

Benedict made no direct reference to his departure. But in his comments to Spanish-speaking pilgrims he asked the faithful to "continue praying for me and for the next pope."

The traditional Sunday window appearance normally attracts a few thousand pilgrims and tourists, but this time city officials prepared for as many as 150,000 people seeking to witness one of Benedict's last opportunities to connect with the masses.

Authorities also used the event as a kind of trial run for the crowds expected to flock to the square in the coming weeks for the next pope's installation.

Following tradition, Benedict's successor will make his first papal appearance by stepping onto the central balcony of St. Peter's Basilica on the square, shortly after puffs of white smoke from the Sistine Chapel chimney tell the world the cardinals have made their secret selection.

On Sunday, extra buses and subway trains ran from Rome's train stations to near the Vatican, and free shuttle vans offered lifts to the elderly or disabled.

Mayor Alemanno has asked Italy's government to put aside its austerity agenda and give Rome a few million euros (dollars) to help pay for security, garbage pickup and other logistics for the Vatican crowds.

On Sunday, several in the crowd were exhausted and shaken by their attempts to get into the square between the metal barriers.

"You can't invite thousands of people and then bottleneck the entrance and exit to the square," said Gianbattista Di Rese, an Italian among the distressed. "Imagine if someone had had a bomb. There could have been hundreds of dead." He got into the square but was stymied trying to get out.

Tourists must go through metal detectors before entering St. Peter's Basilica, but there is no such security to stroll the square.

An Associated Press reporter saw many people give up. Some started to panic and yell at police to do something to ease the bottleneck.

Those who arrived hours before the pope appeared could enter the square with ease for a chance to join in the show of support for him. "We wanted to wish him well," said Amy Champion, a tourist from Wales. "It takes a lot of guts to take the job and even more guts ... to quit."

But some were dismayed that Benedict broke with the centuries-old tradition that popes serve till their last breath.

A youth group Militia Christi (Latin for Christ's Militia) held a hand-painted banner asking the pope to stay. "We are asking him to change his mind. He is the good of the church," said youth GiovanBattista Varricchio.

No decision has been announced on a date for the conclave to elect Benedict's successor, but the Vatican has suggested that it might start sooner than March 15, the earliest date possible under current rules, which require a 15-20 day waiting period after the papacy becomes vacant. This has set off a debate whether such a change could be justified and whether it might benefit Rome-based cardinals who because of their positions at the church's headquarters can count on their acquaintance with cardinals around the world.

"Church law should not be changed on a whim," said the Rev. Thomas Reese, an American Vatican expert. He said changing law "would be disruptive."

On Sunday evening, the pope began a customary week of Lenten period reflection ahead of Easter, and his next public remarks won't come until Feb. 24, when he returns for his final studio window appearance over the square.

In his remarks to the throng Sunday, he told the faithful that during Lent "the church, which is mother and teacher, calls all its members to renew themselves in spirit, to reorient themselves decisively toward God, rejecting pride and egoism to live in love."

Benedict has chosen an Italian cardinal to preach to him and Vatican clergy during closed-door sessions in this week of meditation and prayer. The prelate, Gianfranco Ravasi, heads the Holy See's culture office and is touted by some Vatican watchers as a leading candidate to be the next pope. But other observers contend he is heavily identified with one of the rival blocs of Italian prelates in the Vatican's apparatus, which could hurt his chances.